QUIZ: How Much Do You Know About the Heart?

It may only be the size of your fist, but your heart is one of the hardest-working organs in your body. It beats nonstop — whether you’re running laps, laughing with friends, or fast asleep. This Valentine’s season, show your heart a little love by learning what makes it tick.

Think you know what an artery does? Or how long does it take for blood to complete a full circuit through the human body? Get ready for a quiz full of fascinating facts, surprising science, and a few twists that might make your pulse race!